As approximately 20 cases of PCP per 100 patient-months of HAART would have been expected, d'Egidio et al. determined that the risk of developing PCP while on HAART with a CD4 count <200 cells/μL was significantly different from the risk in untreated HIV (rate difference 9.2%; 95% CI 5.7, 12.8%, p<0.05) [12], [13]. Here, CD4 is linked to pneumocystosis.